Study On Preparation And Properties Of TiN-type Hard Films On Cemented Carbide By Advanced PVD Technology

Coating technology, tool materials, design and manufacturing of tools are three key technologies of cutting tools. As machining towards high speed, high efficient, high accuracy, hard turning etc., better properties would be needed for coatings and tool materials, such as high hardness, good corrosion resistance, high toughness and adhension strength, good wear resistance and thermal stability of high temperature of coatings, high strength and toughness of tool materials, and good physicochemical matching between them. For this, TiN, TiCN and AlTiN hard coatings were firstly deposited on cemented carbide by advanced PVD technology(Advanced Plasma Assisted Arc, APA-Arc; High-ionized Plasma Assisted Coating, HIPAC) of Balzers-Metco in China, with optimized parameters. A variety of modern testing methods were adapted to analysis the main mechanical propertites and key technical indexes, the results were as follows:Based on earlier researches, TiN, TiCN and AlTiN hard coatings(1-fold) were respectively deposited on commercially available mirror-polished YG8 cemented carbide substrates by optimized APA-Arc technology. Graded TiCN hard coating was deposited by increasing C2H2 flow and decreasing bias voltage. AlTiN hard coating was deposited by increasing bias voltage. Morphology observation results show that three coatings were smooth surface with a small amount of particles and pores, and of fine columnar crystals, interlock with substrates, thickness values of three coatings are 6.5μm, 4.2μm and 6.2μm, respectively, deposition rates are quite high. Phase analysis results indicate that TiN hard coating shows(111),(220) lattice planes preferred orientation, TiCN hard coating shows(111) lattice plane preferred orientation, and Al TiN hard coating shows(200) lattice plane preferred orientation. Composition analysis results show that the compositions of three coatings are all close to pre-set compositions, and the atomic ratio of Al/Ti in AlTiN hard coating matchs the target composition. Hardness test results show that the hardness values of three coatings are 24.45 GPa, 34.36 GPa and 33.82 GPa, respectively. Scratch test results show that the coating-substrate adhesion forces Lc2(radius of indenter is 100μm) of them are 19.8N, 21.2N and 24.3N, equalling to 79.2N, 84.8N and 97.2N when the radius is 200μm according to the literature report, respectively. In the corrosion resistance experiment, the protective efficiency is 96.1%, 91.3% and 94.3%, respectively, and in the oxidation experiment under 800℃, thermal stability becomes worse from AlTiN, TiCN to TiN hard coatings. The roughness(Ra) values of three coatings are between 0.16~0.21μm(0.14μm of substrate). Contact angles with distilled water of three coatings are between 68.8?~82.3?.Al0.55Ti0.45 N and Al0.67Ti0.33 N hard coatings were deposited on YT14 cemented carbide substrates by APA-Arc evaporation technologies respectively and Al0.60Ti0.40 N hard coating was made by Platit equipment of a company from Shenzhen, China. Morphology observation results show that Al0.55Ti0.45 N and Al0.67Ti0.33 N hard coatings with less particles, finer pores than that of Al0.60Ti0.40 N hard coating, thickness values of three hard coatings are 7.6μm, 6.0μm and 1.8μm, respectively. The fine columnar grains become finer as the Al content increased and interlock tightly with substrates. Phase analysis results indicate that Al0.55Ti0.45 N and Al0.67Ti0.33 N hard coatings show(200) lattice plane preferred orientation, and Al0.60Ti0.40 N hard coating shows(200),(220) lattice planes preferred orientation. Composition analysis results show that the atomic ratio of Al/Ti in three AlTiN hard coatingsmatchs the target composition. Hardness test results show that the hardness values of three hard coatings are 33.77 GPa, 30.84 GPa and 25.97 GPa, respectively. Scratch test results show that the coating-substrate adhesion forces Lc2(radius of indenter is 100μm) of them are 24.1N, 22.2N and 18.1N which equal to 96.4N, 88.8N and 72.4N when the radius is 200μm according to the literature reports, respectively. In the corrosion resistance experiment, the protective efficiency of them are 77.1%, 84.0% and 61.8%, respectively. Three coatings are quite stable under the oxidation experiment of 800℃. The roughness(Ra) range of three coatings are between 0.13-0.18μm(0.21μm of substrate). Contact angles with distilled water of three coatings arebetween 73.5?~79.0?. In summary, the Al0.55Ti0.45 N hard coating shows the best comprehensive performance.TiN thin films were deposited on YG6, YT14 and N01 cemented carbides by HIPAC technology(2-fold). Morphology observation results indicate that the thin flims and the substrates show conformal morphology, surfaces are smooth, dense and without particles, the thickness values of three thin films are between 350nm~470nm, and there are nanoscale columnar crystals within thin films. Preferred orientations of TiN thin films on YG6 and N01 cemented carbides are(111) and(220) lattice planes, while the preferred orientation on YT14 cemented carbide is(111) lattice plane. Compositional results of three thin films are almost the same. Cross-sectional topographies show that three films are quite dense nanoscale columnar crystals, interlock with substrate. The roughness(Ra) of three films is close to the substrates. Contact angles with distilled water of three filmsare between 89.8?~92.5?.